Vacuum pump



ne@ 13, 1932. J, DUBRWN 91,890,574

VACUUM PUMP Filed May 12, 19:50 2 sheets-shut '1' J. DUBROVIN -VACUUMPUMP QQ. ,QQ Q s NN Q QQ W w ,QW n@ Nm QN bw um, NN

b. mw! QN @CRN NN QQ Patented Dec. 13', 1932 JOHN DUBROVIN, OF CHICAGO,COMPANY, OF CHICAGO,

ILLINOIS, `ASSIGINOR, TO CENTRAL ILLINOIS, A CORPORATION OF ILLINOISSCIENTIFIC VACUUM.' PUMP Application led Hay 12, 193.0. Serial No.451,567.

This invention relates to improvements in vacuum pum s.

It is an obJect of the present invention to provide a simple andeffective backing pump 5 in combination with a high vacuum stage and tocombine the two so that the backing ump becomes in effect a fore-stagefor the igh vacuum cylinder, and to do this without substantiallyincreasing the number of parts required or changingin any materialdegree the bulk of the pump.

It is an object of the invention to allow better cooling than hasheretofore proved possible and to avoid difficulties with the sealingfluid; to secure the rapid outgassing of the oil so that the highestvacua may be quickly attained; to reduce as far as may be practicablethe volume of oil necessary for sealing the pump; and to subject thisfoil continuously to an outgassingv process.

By sealmgl the pump by means of oil channels instead of running itimmersed in a tank of oil, I not only materially reduce the volume ofoil to be outgassed, but I also expose the outer surfaces of the pumpdirectly to the air and, as a direct result, achieve much loweroperating temperatures and a reater capacity for my device. The principes and details of construction will become apparent from thespecification and the annexed figures in which 7 v Fig.` 1 is avertical, longitudinal section through my device;

ig. 2 is a sectional elevation of the same; 1g. 3 is a section throughthe pump taken on the line 3-3 of Fig. 2;

Fig. 4 is a section through the pump taken on the line 4-4 of Fig. 2;

Figs. 5, 6, and 7 are diagrammatic representations of the position ofthe parts in my improved pump in three positions of its operating cycle.

With reference to Fig. 1, the pump is com- 5 posed of a ring section 10,provided with a neck like extension 11 and the end closure plates 12 and13. Both the ring and the plates are ground upon their mating surfaceand the joint thus formed is made as tight J as possible. The ring isprovided with a cylindrical pump chamber 14 in which the eccentric 15aiiixed to the shaft 16rotates.

An inta-ke passage is provided by the bore hole 9, as shown in Fig. 2^.vConnecting with the bore 9 is the intake pipe 61 which is threaded andsealed into the boss 59 on the rng 10. The configuration of the plate 12provides a housing 17 for the bearing 18. The plate 13 is 19 whichprovides a bearing for the shaft. The stud is counz'erbored to receive agland (notshown) which is held in place by the packing nut 21 threadedon the stud.

n eccentric strap 22 surrounds the entire face oi the eccenr'c and bearsa blade 23 operatively connected to the strap in some fluid tight mannersuch as the tongue and groove lock shown. The strap may itself contactwith the cylinder wall, as shown on ig. 2, or the eccentric member maybe made to do the aci'ual contacting necessary and the strap occupymerely a narrow zone thereon.

A gland 24 adapted to oscillae as the movement of er extendinglongiudinally across the gland. For machining reasons only, the gland issectional and is closed by the ca 30. The chamber is divided by theblade into two pump cylinders 25 and 26 in wh'ch the pistons 27 and 28,which are here shown as integral extensionsof the blade, operate. he twopumps exhaust into the space 29 which forms the common exhaust passagevfor both pumps.

The pistons carry the ball exhaust valves 32, 32, the balls being seatedin the passages 31, 31. A light retainer 33,v held in place by screw 34,prevents the balls from being dsp.ace

By reference to Fig. 2, it will be seen that the floor 'of (he cylinder25 forms a sharp angle with the blade and that a portion of it 1s cutaway, as shown at 36, Fig. 1, to form the exhaust passage from therotary stage of the pump. l

- The angular iioor urges a cylindrical valve provided with a hollowstud leaf spring 42 37 against the blade 23. The movement of the valveis limited by the retainer pin 38. The ends of the cylindrical valve 37are slightly chamfered, as at 40, to provide a bypass through which theoil may pass into t e exhaust passage and into the rotary pump sta e.-

he oscillating gland 24 bears an exhaust valve 39 on its upper exposedarea, compose of an upper arcuate spring 41 and a lower These aremaintained in position by the screws 43 and stops 44.-

As indicated on Fig. 2, the intake passage 45 tothe pump cylinder 26leads to a groove 46 which may be in either the mating surface of thering 10 or of the plates 12 and 13. An extension of the groove formed bya drilled passage 47 leads up to the shaft 16 and is connected with thegrooves 48, 48 cut on the shaft.

In order to counterbalance the device, it is usuall preferable to hollowout the rotor 15, as is s own at 49. The plate 12 accordingly bears anannular groove 51 cut in its inner face surrounding, ut spaced from theshaft 16. The groove 51 is connected by a groove 52 to the suction spaceof the pump.

An oil trap member 53 heldin position by the screws 54 forms the coverof the device. A asket 55 is interposed between the trap and pump casingto prevent leaks. The bottom of the trap is broken by a tendintransversely across it, and rising from t e edge ofthe channel are twooil retaining and baflie members 58 and 59 which also extend across thetrap. Two oil level regulating nipples 61, 62 with longitudinal passagestherethrough 63, 64, are forced into the, bottom wall of the trap. AV-shaped baiile 56 covers the channel 57 and forms a spray hood. A sightglass 65 is provided in one wall of the trap. The bezel 66 drawn up bthe screw 67 presses the glass up against the exible gasket 68. Theoutlet from the ump is provided by the orifice 69.

The Figs. 2, 5, 6 and 7 illustrate the position of the operative partsat intervals in one cycle of the pump.

The operation of the pump is as follows: Starting with the position ofthe device as shown in Fig. 2, as the shaft rotates in a clockwisedirection, the eccentric causes di ferent portions of the eccentricstrap to come pro ressively in contact with the cylinder walMomentarily, there is but one space within the cylinder (Fig. 2)equalizing the gas ressure therein, and then the space is cut 1n two(Fig. 5). Thereafter, (Figs. 6 and 7), the space to the right (ahead ofthe piston aspirates the gas. The space to the left, hind the piston)compresses it.

i Since the eccentric carries the eccentric stra first to one side, thento the other, the bla e which is a rigid extension of the strap mustswing from side to side. Accordingly,

channel 57 ex- `in the gland. The upstroke o d the the gland which formsa stu'mg box preventing the gas on the com ress1on side from mixing withthe gas on t e intake side must oscillate andthe blade ride up and downwhich bears the pistons on its upper end creates a suction in the pumpchambers 25 and-'26. The gas Ibein exhausted through passage 36 is un ercompression and rushes in to fill the 'space 25.

When the article to be exhausted is nearly at atmospheric pressure, theamount of gas handled by the .eccentric stage is greater than thereciprocating stage can actually pump. Both valves in the reciprocatingsta e are accordingly displaced and a constant ow of gas maintainedthrough the passage and piston. However, when vacua of any substantialdegre'e requiring a fore-pump are approached, the amount of gas deliverethrough the port 36 is. not suilicient to overload the chamber and theeiiicac of the forepump then begins to be felt an increases asincreasing vacua are obtained.

Because of the great range of both volume and pressure which a vacuumpump commonly encounters, considerable diliiculty has been experiencedwith valves. The use of a ball valve in the reciprocating piston is,however, particularly helpful since the valve is operated not by thepressure against the seat,

f the blade but by its own inertia and will respond although very smallquantities of gas are expelled as the higher vacua are approached. Thepiston may thus act as a scavenger without unduly compressing the gas inthe cylinders 25 and 26.

On standing, oil seeps into the cylinder. When the pump is started,slugs of oil Iand gulps of air practically at atmospheric pressure passthrough the device. A relief valve is thus a necessity. The valve 39 isboth a relief valve and a differentially responsive exhaust valve.

When the pressure in the space is high, as when tra ped oil oratmospheric air is passing, the owed spring is forced up and the leafvalve rises on its guide studs exposing a wide slot. As the pressuredrops, the leaf valve remains seated, but since it is very thin andflexible (it may even be ta er ground to aid in this effect), it is deected over smaller and smaller areas. Thus the effective opening of thevalve is secured at pressures so low that .operation of a gravityinertia or fixed tension spring valve becomes uncertain.

In order to balance the eccentric to allow high speed operation of thepump, av hollow space in the body of the eccentric is provided. Uponstanding, this space will build up to atmospheric pressure and sincepumps which are capable of producing very high vacua are nice mechanicaljobs, the fit between the yrotor and the plates 12 and 13 is necessarilyclose and practically sealed by tween the shaft and `into the highvacuum the oil film therebetween. An evil known as' slipping then mayoccur,'since the as con-A tained in the hollow slowly leaks into `thehigh vacuum area. This is prevented in the present pump by the provisionof the annular passage 51 (which may be 1n either of the end plates) andthe connecting passage A52. The e'ectof this is to add the space withinthe body of the eccentric to the space to be evacuated and, since the,gas within the s ace is pulled down to the tpressure of the igh vacuumchamberyno slipping can occur.

To` prevent leaks, it is desirable to reduce the pressure diHerentialexisting between the outer and the inner edges of the mating faces andin 'fact at any joint in the pump where leaks could occur. The channel46 is accordingly cut into the face of the plates 12 and 13 or into thering 10, as may be desired. The channel is connected by the passage 45to the second reciprocating pump 26 contained in the gland. 'llheextension of the channel 47 connecting with grooves 48 allows thisvacuum seal to be applied to the joint bepacking.

The vacuum in the chamber 26 and the sealing channels 46 is in the orderof millimeters. Consequently, the pressure tendlng to make the pumpcasing leak exists as a gradient between `the outer surface and'thesealing channel. Whatever air leaks into the pump along the joints inthe casing 1s consequently trapped in the sealing channel and swept out.rthe residual gradient between the sealing channel and the high Vacnumchamber is small. It will cause no trouble if the joints are wellmachined and usual sealing precautions are taken.

Upon first glance, it would seem as if no passages were provided throughwhich sealing and lubricating `oil could be led to the moving parts. Inthis pump, however, all free fits are open oil passages, for it must beremembered that the oil is under a pressure of more than 14 referred toany space below the pistons, that it meets no obstruction of trappedgas, and that it spreads and creeps over every surface.

@il will adsorb gas in considerable quantities whenever it is exposed toa gaseous atmosphere. lf such oil then were admitted chamber, the gaswould be delivered up and of vacuum obtainable would dependfupon thefreedom from adsorbed gases which the sealing medium enjoyed. In orderto pre-` vent such .polluted oil from working into the igh vacuum stage,it is necessary to expose it to a degree of vacuum suflicient to causeit to deliver up the major portion of the gas before it can reach thechamber.

Whatever oil comes in under the valve 39 and passes down the walls ofthe reciprocatingl pumps into the high vacuum pump chamlbs. to the sq.inch, as'

consequently the degree ber will have been very thoroughly vacuumtreated .i by the reciprocating stage. However, there is' another pathby wh1ch the oil can get into the high vacuum chamber and that l1s alongthe joint between the gland andl the casing. It 1s advantageous,therefore, to provide one or more longitudinal channels in the bearingface between the casing and gland and connect these channels to the en-4trapment channel system 46. It may even prove advantageous to makearcuate transverse extensions to this channel as shown at 71, 72, Fig.2, so that more oil may be trapped and subjected to vacuum. Whateveroil, therefore, reaches the high vacuum stage has been robbed of theadsorbed gas by this precaution.

pon starting a new pump, it is necessary to pour in through the opening69 a quantity of oil suliicient to rise up to the top of the nipples 61,62, and in addition an amount which Willill the sealing channels andsufiiciently seal and lubricate all of the working parts. It will be thetendency of the working parts to squeeze and force out some of vthis oilwhich will be blown against the baille as a spray, but whatever oildrops olf the balile will cause an overflow of the reservoir and theexcess will pass through the channels 63, 64 back into the movingsystem.

have described my improved design as applied to a vacuum pump capable ofproducing vacua of very high degree. Such a pump will produce vacua oftheorder of l/1.0,000 of a millimeter without difficulty.

It 1s, of course, obvious that the be decidedly useful in other work.

Where high vacua are not desired or a pump for liquids needed, thechannels 51, 52, 45 and 46 are not necessary, and a passage may bedrilled through the blade just below the piston so as to cause the twosides of the piston to operate in parallel upon the fluids discharged bythe rotary stage.

I do not limit myself to a precise arrangepump will ment, for it isobvious that modifications and rearrangements action is in full hereinset forth.

I claim as my invention 1. A vacuum pump of the rotary plunger typecomprising a casing and a pump cylinder having inlet andexhaustpassages, in combination,an eccentric in the cylinder, an eccentricstrap, a blade separating-the inlet and exhaust chambers of thecylinder, operatively connected to the strap, an oscillatmay be made inwhich the accord with the principles ing gland within the casing formingan oscil' l'ating pump cylinder in which the blade reciprocates, apiston carried by the blade, the inlet passage to the reciprocatingstage forining the exhaust passage of the first named stage, and a valveclosing the passage.

2. A Vacuum pump of the rotary plunger type comprising, in combination,a plunger haust valve closing Eil r tion, an eccentric in the cylinder,

member provided with \a radial blade, an oscillating gland cooperatingwith the blade and having a pump cylinder therein, a piston in the pumpcylinder, a connection between the piston and the radial blade causingthe piston to reciprocate, and an inlet passage to the pum cylinderreceiving material discharged by the rotary .plunger stage of the pump.Y l

3. A vacuum pui'np comprising, in combination, a casing having acylindrical chamber, an inlet thereto, an eccentric rotor in thechamber, an annular piston surrounding the rotor and rovided with aradial blade rigidly atlixed t ereto, a gland adapted to oscillate andin which the blade reciprocates, a cylinder in the oscillating gland, apiston in the oscillating cylinder operated b 1 the blade, an outletpassage lfrom the cylin rical chamber communicating with the inlet tothe oscillating cylinder, and a valve in the passage.

4. In a pump of the rotary plunger type, including a casing and a pumpcylinder having inlet and exhaust passages, in combinaan eccentricstrap, a blade operatively connected to the strap separating the inletand exhaust chambers of the cylinder an oscillating gland within thecasing orming an oscilating pump cylinder in which the bladereciprocates, a piston carried by the blade, the i inlet c passa e beingthe e to the reciprocating stage aust passage of the first nam stage, avalve closing the passage, and a bypass around the valve through whichsealing` fluid may be admitted to the pump chamber.

5. In a pump of the rotary plunger type including a casing and a pumpcylinder having inlet and exhaust passages, in combination, an eccentricin the cylinder, an eccentric strap, a. bladeseparating the inlet andexhaust chambers of the cylinder operatively connected to the strap, anoscillating gland within the casing forming an oscillating pump cylinderlin which the blade reciprocates, a piston carried by the blade, theinlet passato the reciprocating stage forming the ex aust passage of thefirst named stage, a valve closing the passage, inertia valves carriedby the piston, and a leaf spring exthe oscillating cylinder.

6. A vacuum pump of the rotary plunger type, comprising, in combination,a casing, a cylinder therein provided with intake and exhaust passages,a hollow eccentric within the cylinder, and an annular eccentric strapsurrounding the eccentric, a blade operatively integral with the strap,and a channel in the casing extending from the suction space andintercepting the path swept by the hollow of the rotor whereby the spacewithin the rotor may be reduced to, and maintained substantially at,the-same pressure as that existing in the suction passage of the pump.

7. A vacuum pump of the rotary plunger ing liquid in type, comprising acasing made of joined parts containing a pump cylinder wherein a bladeattached to an eccentric strap is caused to operate a reciprocatingpump, channels formed in the components of the casing and interposed inthe mating face between the joined parts, a sealing iuid within thecasing and the channels, a cylinder in the reciprocating stage adaptedto outgas the sealing medium, and a connection between the channels andthe outgassing pump.

8. In a vacuum pump of the rotary plunger type comprising a casing madeot joined lparts containing a pump ,cylinderv wherein a blade attachedto an eccentric strap is caused to operate a reciprocating pump, meansfor preventing leakage along joints in the casing and packing memberswhich consists oi channels formed in the components of the casing andinterposed in the bearings and in the mating faces of the joined parts,a sealthe channels and a connection between the reciprocating pump andthe channels for producing a vacuum therein, whereby the pressuregradient tending to cause leaks into the high vacuum space isInaterially reduced and the sealing liquid is outgassed.

9. A multi-stage vacuum pump of the rotary plunger type comprising acasing sealed against leaks by a liquid, va. high vacuum pump c linderformed in the casing, an eccentric in the cylinder, an oscillating glandjournaled inthe casing and a pump cylinder formed in the oscillatinggland, means to ap- -ply a preliminary vacuum between the gland andcasing and to outgas the sealing liquid before its entrance into thehigh vacuum cylinder, which consists of channels in the bearing surfacebetween the casing and gland, and a connection to the intake of theoscillating pump cylinder.

10. In a multi-stage vacuum pump of the rotary plunger type, a liquid, acasing, a cylindrical oscillating member journaled in the casing, a pumpcylinder formed in the oscillating member, a blade connected to therotary plunger and caused to reciprocate in the oscillating membei', twopistons carried by the blade, which blade together with the walls of theoscillating member forms two pump chambers therein, one chamber beingthe exhaust passage of the rotary plunger pump, the other serving tooutgas the sealing medium of the pump.

11. In a vacuum pump including a casing wherein the amount of fluid andthe pressure at its discharge vary through wide limits, having a xedrotary pump cylinder and an oscillating reciprocating pump cylinderwithin the casing, the combination of valves in the reciprocating memberoperated by inertia and an exhaust valve for the oscillating sealedagainst leaks by cylinder adapted to open a diierent amount i withdiffering pressures and volumes of the exhausted Huid.

2. In a vacuum pump provided with a piston chamber, a piston for saidchamber, an intake and a discharge port for said chamber, a valve forsaid discharge port,

same, said chamber having an opening for conducting oil from said oilreceptacle to said chamber and a baie above said oil retaining' membersfor defecting` oil splashed from said oil chamber by air dischargedthrough vsaid outlet port into said receptacle.

n testimony whereof I aX my signature.

JOHN DUBROVIN.

